A typical endoscope comprises a cylindrical stainless steel case enclosing a bundle of optical fibers extending between a distal end (tip end) and proximal end of the endoscope for transmitting light through the endoscope. A fiber optic cable delivers light from a light source into the case through an aperture situated near the proximal end of the endoscope. The optical fibers transmit the light through to the distal end, where the light exits the endoscope and illuminates the area near the distal end. The endoscope in turn transmits an image of that area through a rod and lens system to an eyepiece lens at the proximal end. A video camera coupled to the eyepiece converts the image into electronic signals and transmits the signals to a video monitor, where the image is displayed.
Endoscopes are used most often in "minimally invasive surgery", in which an endoscope is inserted into a patient, allowing a surgeon to illuminate and view the interior of the patient with minimal penetration. The use of endoscopic surgery is growing, in large part because it is generally safer and less expensive than conventional surgery, and patients tend to require less time in a hospital after endoscopic surgery. Conservative industry experts estimate that about 4 million minimally invasive procedures were performed in 1996. As endoscopic surgery becomes more common, there is an increasing need to accurately evaluate the performance characteristics of endoscopes.
To obtain a true measure of the performance of an endoscope, both the lens and the optical fibers should be evaluated. For example, some optical fibers may be damaged and only partially transmit light. In addition, the lens may distort images or blur the sharpness of image colors. These and other shortcomings in the optical performance of endoscopes may be the result of imperfections in the manufacturing process and/or may develop as the endoscope is used over time.
An apparatus for evaluating the performance characteristics of endoscopes would be able to validate claims made by endoscope vendors about the capabilities of their products. Accordingly, such an apparatus would be advantageous for the purchasers and users of endoscopes. In addition, such an apparatus would be of great use in evaluating disposable endoscopes, which currently have an average life of about 20 to 30 uses. An apparatus for evaluating the performance characteristic of endoscopes would be able to determine when a disposable endoscope is so degraded that it should be discarded.
Furthermore, an endoscope may be adequate for one surgical procedure but inadequate for another which requires more precision, such as when a patient is bleeding. Currently, an endoscope which is suspected of having any deficiency must be removed from service and sent for repair, which can be both costly and time consuming. An apparatus for evaluating the performance characteristics of endoscopes would preferably be able to identify endoscopes which are appropriate for one type of procedure although inadequate for another.
Such an apparatus would also be most advantageous in a program of preventative endoscope maintenance. Endoscopes cost thousands of dollars, and typically require repairs at least about twice per year which can cost several thousand dollars per repair. There is a need for a tool for evaluating the performance characteristics of endoscopes, thereby verifying if repairs have been effective.
An apparatus for evaluating endoscope performance ideally would also be able to store the results of past tests and evaluations, thereby allowing the system to evaluate changes in endoscope performance after repair operations and over the lifetime of the endoscope. In addition, such information on changes in endoscope performance would be useful in predicting changes in the performance of other endoscopes before their performance degrades. This would help predict future endoscope needs.
The present inventors are not aware of any commercially available tools for use in a clinical environment which quantitatively assess the performance characteristics of endoscopes.
A further complication is that endoscopes vary in length, diameter and tip angle, which is the angle between the direction of view and the longitudinal axis of the endoscope. A system for evaluating endoscope performance would ideally also be able to accommodate endoscopes which have varying optical and/or physical characteristics.
Accordingly, it is an object of the present invention is to provide a method and apparatus for evaluating the optical performance characteristics of fiber optic endoscopes.